Deceleration device and valve mechanism

ABSTRACT

An improved deceleration device for a hydraulic cylinder is taught. An end cap seals off the end of a housing adjacent which a plunger of the hydraulic cylinder is positioned when in one of its terminal positions. A groove is formed on the surface of the end cap facing into the plunger housing. A hydraulic passage forms a portion of the end cap and a passageway interconnects the groove and the hydraulic passage. A groove covering device is provided which covers the groove of the end cap when in covering relationship thereto. The groove covering device has an orifice therein which overlies the groove of the end cap when in covering relationship thereto. The groove covering device is resiliently mounted on the plunger in facing relationship to the groove. The resilient mounting spaces the groove covering device a sufficient distance from the plunger that the groove covering device covers the groove prior to the plunger reaching the end of its travel to its retracted position.

D United States Patent 91 [111 3,885,654

Hauswirth May 27, 1975 DECELERATION DEVICE AND VALVE Primary ExaminerGeorge E. A. Halvosa MECHANISM Attorney. Agent, or Firm-William E. Johnson; Keith [75] Inventor: Vernon O. Hauswirth, Madison Zerschlmg Heights, Mich. [73] Assignee: Ford Motor Company, Dearborn, [57] ABSTRACT Mich. An improved deceleration device for a hydraulic cylinder is taught. An end cap seals off the end of a hous- [22] 1974 ing adjacent which a plunger of the hydraulic cylinder [21] Appl. No.: 458,379 is positioned when in one of its terminal positions. A groove is formed on the surface of the end cap facing I into the plunger housing. A hydraulic passage forms a [52] US. Cl. 188/2849, 113G561 l98180339252, portion of the end cap and a passageway interconnects the groove and the hydraulic passage. A groove cover- [51] Int. Cl Fl6f 9/34, Fl6f 9/48 ing device is provided which covers the groove of the [58] Field of Search l88/322, 284, 311', 91/406,

end cap when in covering relationship thereto. The 91/394, 395, l6/5l, 52, 66, 84

groove covering device has an orifice therein whlch inferences Cited overlies the groove of the end cap when in covering relationship thereto. The groove covering device IS re- UNITED STATES PATENTS siliently mounted on the plunger in facing relationship 2.6l9.199 95 ch a y 188/284 to the groove. The resilient mounting spaces the Tucker groove covering device a sufficient distance from the 3,034,482 5/1962 9l/395 plunge, that the groove covering device covers the 3,470,986 8/1969 Whisler, Jr l88/3l7 X groove prior to the plunger reaching the end of its travel to its retracted position.

2 Claims, 5 Drawing Figures DECELERATION DEVICE AND VALVE MECHANISM BACKGROUND OF THE INVENTION In the operation of a hydraulic cylinder in which a plunger is mounted for movement between an advanced position and a retracted position in a housing, it is desirable to decelerate the plunger just prior to its reaching the terminal end of its stroke to either an advanced position or a retracted position. The desirability of effecting this deceleration comes about from the fact that if it is not accomplished, the piston moves with a greater force into engagement with those stop surfaces which define the retracted position or the advanced position causing an impace load on such stop surfaces and supporting structure. By employing a deceleration device, the travel of the piston from one position to another may be accomplished at a rapid rate with a high force load but the inertia developed from this force is substantially dissipated before the piston acts against the stop surfaces. By reducing the force which is dissipated by the piston on the stop surfaces, an increase is achieved in the useful life of the hydraulic cylinder.

It is also desirable to construct such deceleration devices as simply as possible. Simple construction of such devices insures their use as an additional portion of a hydraulic cylinder as the entire cost of the structure is not increased greatly. A simple design for such a com struction insures reliability of such a deceleration device over its intended operational life.

SUMMARY OF THE INVENTION This invention relates to an improved deceleration device for a hydraulic cylinder and, more particularly, to an improved deceleration device for a hydraulic cylinder having a housing and a plunger mounted within the housing for movement between terminal positions, such as an advanced position and a retracted position.

In accordance with the teachings of this invention, the improved deceleration device is fabricated at either or both ends of the hydraulic cylinder as follows. An end cap seals off the end of the housing adjacent which the plunger is positioned in one of its terminal positions. A groove is formed on the surface of the end cap which faces into the housing. A hydraulic passage is formed in the end cap and it is connected to the groove by a passage. A groove covering device is employed for covering the groove entirely when the device is in covering relationship thereto. An orifice is provided in the groove covering device, which orifice overlies the groove when the groove covering device is in the covering relationship thereto. A resilient structure mounts the groove covering device on the plunger in facing relationship to the groove of the end cap. The resilient structure spaces the groove covering device a sufficient distance from the plunger that the groove coverng device covers the groove prior to the plunger reaching the end of its travel to its terminal position.

By use of the improved deceleration device, the following function is achieved. When the plunger is moved towards its terminal position, the groove of the end cap conducts fluid within the housing, in the volume between the end cap and the plunger, to the passage for exhausting of that fluid from the housing. When the groove covering device covers the groove, the fluid within the housing is exhausted initially from the housing through the restricted orifice in the groove covering device and then to the passage. This action reduces the fluid exhausting rate from the housing causing an increase in the pressure of the fluid within the housing as the plunger approaches its terminal position. The increase in pressure, of course, causes a deceleration of the plunger as it approaches its terminal position. The deceleration action reduces the force which is applied by the plunger on stop surfaces which define the terminal position of the plunger.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view, partly in cross section, showing the improved deceleration device of this invention in a hydraulic cylinder. In FIG. I a pistion of the hydraulic cylinder is shown as it is moving toward a terminal, retracted position.

FIG. 2 is a view similar to FIG. I but it shows the deceleration device of this invention as the device becomes effective to decelerate the plunger moving to its retracted position.

FIG. 3 is a view similar to FIG. 1 but showing the plunger of the hydraulic cylinder in its retracted position.

FIG. 4 is an exploded view taken from the circled area of FIG. 3 showing some of the details of the deceleration device.

FIG. 5 is a view taken in the direction of arrow 5 of FIG. 4 showing some further details of the deceleration device of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Construction In the figures of the drawings, a hydraulic cylinder is generally identified by the numeral 10. Since such cylinders are well known in the art, only the components thereof associated with the improved deceleration device will be described in detail. The hydraulic cylinder includes a cylinder 12 and a piston 14 mounted for movement in the cylinder between terminal position, that is a retracted position and an advanced position, by the admission of, or exhausting of, hydraulic fluid from the front or rear of the piston. The piston has a face 16 which is brought into contact with an annular stop surface 18 formed on an end cap 20 which, in turn, closes one end of the cylinder. When the face of the piston is in contact with the annular stop surface, the hydraulic cylinder shown is in its terminal, retracted position. While the deceleration device of this invention is shown as being associated with the piston in its retracted position, a similar device may also be used on the other end of the cylinder at a location associated with the advanced position of the piston.

The purpose of the deceleration device of this invention is to limit the force with which the face 16 of the piston 14 is brought into engagement with the annular stop surface 18. If the piston is brought into contact with the stop surface repeatedly with full force thereon, damage is done to the stop surface as well as to the end cap and the piston itself. This damage may be reduced by use of the improved deceleration device of this invention.

An annular groove 22 is formed symmetrically about the central axis of the end cap 20. A passage 24 connects annular groove to a hydraulic body portion of a relief valve 26. The passage 24 also connects the annular groove to a hydraulic outlet passage 28 which is, in

turn, connected to the hydraulic supply (not shown) supplying the hydraulic cylinder 10. The relief valve 26 closes a valve opening 30 which is connected to a port 32 which, in turn, is connected to a hydraulic fluid containing volume 34 defined between the face 16 of the piston 14 and the end cap. The relief valve permits fluid to be exhausted from this volume when the pressure therewithin exceeds relief valve pressure.

A ring member 36, having a central opening 38 therein, is secured by an overturned lip 40, as best seen in FIG. 4, to a large end of a spiral spring 42. A small end of the spiral spring is held by a bolt 44 and a clamping plate 46 to the face 16 of the piston 14. The ring member is sufficiently wide, between its inner and outer diameters, to cover the annular groove when in covering relationship thereto. This ring member also has one or more restricted orifices 48, best seen in FIGv 5, which are in registry with the annular groove on the end cap when the ring member is in coverng relationship thereto.

Operation FIG. 1 shows the hydraulic cylinder in such a condition that the piston 14 thereof is being moved to the left in order to bring the face 16 of the piston into contact with the annular stop surface 18 at the terminal, retracted position of the piston. As the piston approaches this position, hydraulic fluid in the volume 34 is being forced through the annular passage 24 and the outlet passage 28. 1f the pressure in the volume exceeds the operating pressure of the relief pressure valve 26, fluid is also exhausted from the volume 34 through the port 32 and the valve opening 30.

The spiral spring 42, which mounts the ring member 36 in front of the face 16 of the piston 14, is sufficiently large that the ring member is brought into contact with the end cap 20 to cover the groove 22 prior to the time that the face of the piston has contacted the annular stop surface 18. This condition is shown in FIG. 2. When this condition occurs, the hydraulic fluid being exhausted from the volume 34 is reduced in its rate of exhausting because it must pass initially through the orifice 48 formed in the ring rnember prior to exiting through the passage 24 and the outlet passage 28. Thus the pressure of the hydraulic fluid within the volume 34 begins to build prior to the time that the face of the piston has come into contact with the stop surface.

As the piston 14 of the hydraulic cylinder 10 continues its leftward movement from the position shown in FIG. 2 in order to bring the face 16 of the piston into engagement with the annular stop surface 18, the spiral spring 42 collapses allowing a relative movement between the ring member 36 and the piston. The spiral spring maintains pressure on the ring member to hold it in engagement with the groove 22 whereby pressure continues to build within the volume 34. As the pressure builds within this volume, a resistive force is applied to the piston 14 and its rate of movement is decelerated so that it is brought more gently into contact with the stop surface. If at any time during this deceleration process, the pressure within the volume 34 exceeds the relief valve 26 pressure, a relief for the hydraulic pressure is provided by opening of the valve and exhausting the fluid through port 32, the valve opening 30 and the outlet passage 28.

The piston 14 may be operated in the reverse direction when a positive pressure is applied by hydraulic fluid coming in through the outlet passage 28, the passage 24 and the annular groove 22. The pressure acts to lift the ring member 36 away from the groove and to start the movement to the right as viewed in FIG. 3. This action moves the piston from its terminal, retracte'd position toward the other terminal position which is its fully advanced position.

There has been described herein an improved deceleration device for a hydraulic cylinder which is simple to construct and efficient in operation. Others skilled in the art will develop modifications of this improvement which will fall within the spirit and scope of this invention. It is intended that all such modifications fall within the scope of the appended claims.

I claim:

1. An improved deceleration device for a hydraulic cylinder which has a piston mounted for movement in the cylinder between terminal positions, the deceleration device comprising:

an end cap of circular shape sealing off the end of the cylinder adjacent which the piston is positioned when in one of its terminal positions;

an annular groove formed on the surface of the one end cap facing into the cylinder, the groove being symetrical about the central axis of the end cap;

a hydraulic passage forming a portion of the end cap;

passage means for connecting the annular groove to the hydraulic passage;

a ring shaped plate having a dimension between an inner diameter and an outer diameter thereof greater than the width of the annular groove so that the groove is covered when said ring shaped plate is in covering relationship therewith;

at least one small opening through said ring shaped plate;

a spirally wound spring secured at one end to the face of the piston and at the other end to the ring shaped plate, the spirally wound spring spacing the ring shaped plate a sufficient distance from the piston that the ring shaped plate covers the annular groove prior to the piston reaching the end of its travel to its terminal position;

whereby when the piston is being moved towards its terminal position the annular groove conducts fluid within the cylinder in the volume between the end cap and the piston to the passage means for exhausting of that fluid from the cylinder, and whereby: when the ring shaped plate covers the annular groove, fluid within the cylinder is exhausted initially from the volume through the small opening in the ring shaped plate and thence to the passage means thereby reducing the fluid exhausting rate from the cylinder to cause a deceleration of the pis ton as it approaches its terminal position.

2. The deceleration device as defined in claim 1 wherein:

a relief valve is provided for interconnecting the volume between the end cap and the piston and the hydraulic passage so that the pressure within the volume does not exceed a predetermined level. 

1. An improved deceleration device for a hydraulic cylinder which has a piston mounted for movement in the cylinder between terminal positions, the deceleration device comprising: an end cap of circular shape sealing off the end of the cylinder adjacent which the piston is positioned when in one of its terminal positions; an annular groove formed on the surface of the one end cap facing into the cylinder, the groove being symetrical about the central axis of the end cap; a hydraulic passage forming a portion of the end cap; passage means for connecting the annular groove to the hydraulic passage; a ring shaped plate having a dimension between an inner diameter and an outer diameter thereof greater than the width of the annular groove so that the groove is covered when said ring shaped plate is in covering relationship therewith; at least one small opening through said ring shaped plate; a spirally wound spring secured at one end to the face of the piston and at the other end to the ring shaped plate, the spirally wound spring spacing the ring shaped plate a sufficient distance from the piston that the ring shaped plate covers the annular groove prior to the piston reaching the end of its travel to its terminal position; whereby when the piston is being moved towards its terminal position the annular groove conducts fluid within the cylinder in the volume between the end cap and the piston to the passage means for exhausting of that fluid from the cylinder, and whereby: when the ring shaped plate covers the annular groove, fluid within the cylinder is exhausted initially from the volume through the small opening in the ring shaped plate and thence to the passage means thereby reducing the fluid exhausting rate from the cylinder to cause a deceleration of the piston as it approaches its terminal position.
 2. The deceleration device as defined in claim 1 wherein: a relief valve is provided for interconnecting the volume between the end cap and the piston and the hydraulic passage so that the pressure within the volume does not exceed a predetermined level. 